1. Field of the Invention
This invention relates to an image reading apparatus for use in a thermal transfer-type copying machine, and more particularly to an image reading apparatus for reading an image projected from a transparent original.
2. Description of the Related Art
In general a thermal transfer-type copying machine comprises an image reading apparatus that reads an original image and converts the same into electric signals. Further, the machine comprises a signal processing unit that processes the thus converted image signals in a prescribed manner. The machine further comprises a printer unit that prints a desired image on a sheet in accordance with information based on the thus processed image signal. A conventional image reading apparatus is provided in the upper portion of a thermal transfer-type copying machine. The image reading apparatus comprises an original table made of glass, an original table cover that covers or exposes the glass original table, and image reading means provided under the original table. The image reading means reads the image of an original set on the glass original table 3, and converts the same into electric signals.
An adapter has a reflector, a projection opening, and a projector. These are used when the image on a transparent original, such as a developed positive film, is copied. Image projection light from the projector is reflected downward by the reflector Thus, the image on a film original is projected and focused on the original table. The thus focused image is converted by the image reading means into electric signals. Thereafter, a desired image is formed on a sheet using techniques well known to those skilled in the art.
In the above-described conventional image reading apparatus, the adapter having a reflector and projection opening is simply placed on the glass original table. Thus, the optical axis of the reflector will inevitably be shifted by even a small external force on the machine. In addition, the image on a film is read with the original cover left open. Thus, stray light can easily penetrate into the projection opening. Moreover various kinds of projectors may be placed on the glass original table for image projection, potentially resulting in the damage of table.